In order to demonstrate the impact of distribution of users with respect to the location of the dual-functional
active RIS, in Fig. REF  we compare the sum-rate versus the number of users in \(\mathcal {K}_\mathrm {r}\) , in which
the users are randomly located on circle centered at the active RIS. We can see from Fig. REF  that the sum-rate is maximized when users are near equally distributed on the two sides of the RIS. For
comparison, we also investigate the performance of current reflective-only active RIS (RO-ARIS) proposed in [1]}, [2]}. It is noted that, in RO-ARIS assisted communication system,
the sum-rate increases linearly with the number of users in \(\mathcal {K}_\mathrm {r}\) , since it can only assist the
communication of the users within the same half-space as BS. However, the proposed dual-functional RIS can always provide satisfactory sum-rate performance for different user distributions.
